In terms of warfarin therapy, what is the expected dose requirement for a patient with CYP2C9 *2*3 and VKORC1 G>A genotyping results?

The expected dose requirement for a patient with the CYP2C9 23 and VKORC1 G>A genotyping results is indeed less than 5 mg daily. This is based on the pharmacogenetics of warfarin metabolism and sensitivity.

Individuals who carry variants of the CYP2C9 gene, specifically the *2 and *3 alleles, have reduced enzyme activity. These variants result in slower metabolism of warfarin, leading to an increased risk of accumulation of the drug and subsequent bleeding complications if standard doses are administered. Therefore, a lower dose is typically required to achieve the desired anticoagulation effect while minimizing the risk of adverse events.

Additionally, the VKORC1 G>A genotype is associated with warfarin sensitivity. The presence of the A allele leads to decreased expression of the vitamin K epoxide reductase enzyme, which is the target of warfarin, thus requiring a lower dose to achieve therapeutic anticoagulation.

In summary, due to the combined effects of the CYP2C9 23 polymorphisms that decrease metabolic clearance and the VKORC1 G>A genotype that increases sensitivity, the expected warfarin dose for this patient would indeed be less than 5 mg daily.